This activity provides students with a visual for adding and subtracting integers and helps students understand that subtraction can be thought of as adding the opposite. A hot air balloon begins with a certain number of helium bags (providing lift) and the same number of sand bags (providing weight). The vertical position of the hot air balloon is determined by adding or removing a number of helium bags (representing positive integers) and sand bags (representing negative integers).

This material is based upon work supported by the
National Science Foundation under Grant DUE-0226284.
Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s)
and do not necessarily reflect the views of the
National Science Foundation.